1. Field of the Invention
The present invention relates to a broadband connectionless data service provided to realize a local area network (LAN) interconnection, and more specifically to a subscriber information processing method in the service.
2. Description of the Related Art
For example, a switched multi-megabit data service (SMDS) is well-known as a broadband connectionless data service for the purpose of realizing a LAN interconnection.
An efficient process of subscriber information is a very important point in the broadband connectionless data service because a connectionless data service are handled for a large number of users.
FIG. 1 shows the typical configuration of the SMDS system.
The SMDS refers to a connectionless data service based on an asynchronous transfer mode (ATM) system.
Subscriber information is processed through a subscriber network interface (SNI). A subscriber is provided with, for example, a DS1 subscriber loop 101 having a transmission rate of 1.5 Mbp (mega bits per second), and a DS3 subscriber loop 103 having a transmission rate of 45 Mbps. The DS1 subscriber loop 101 is connected to a DS1 terminating circuit 102, while the DS3 subscriber loop 103 is connected to a DS3 terminating circuit 104.
When communications are established through an SMDS, a cell transmitted from a subscriber is assigned a semi-permanent virtual channel identifier (VCI) and a virtual path identifier (VPI) pertaining to the SMDS. The DS1 terminating circuit 102 and the DS3 terminating circuit 104 extracts the cell assigned the semi-permanent VCI+VPI, replaces the VCI+VPI of the cell with a semi-permanent VCI+VPI pertaining to each terminal circuit, and outputs the cell to a switch unit 108.
The cell is inputted to the switch unit 108 through multiplexer/demultiplexer 105, 106 or 107. The switch unit 108 transmits to an SMDS message handler (SMDS-MH) 113 the cell assigned the semi-permanent VCI+VCP pertaining to the DS1 terminating circuit 102 or the DS3 terminating circuit 104.
The SMDS MH 113 is connected to the switch unit 108 through a highway 116 having a transmission rate of 622 Mbps. The SMDS-MH 113 comprises an interface 114 and a line processor (LP) 115, and can include 4 message shelves (MESH) at the maximum, each having the performance of 155 Mbps. One LP 115 can process subscriber information in DS1 subscriber loops 101 of 32 at the maximum permitted in the present station. Therefore, one SMDS-MH 113 can process subscriber information in a total of 128 (32.times.4) DS1 subscriber loops 101. The SMDS-MHs 113 of the number depending on the scale of its own station are connected to the switch unit 108 through the highway 116.
The LP 115 can recognize which terminating circuit the cell has been inputted from, the DS1 terminating circuit 102 or the DS3 terminating circuit 104, by determining the semi-permanent VCI+VPI assigned to the received cell. Then, the LP 115 extracts a source address SA from the message (packet) transmitted through a plurality of cells, and calculates a degenerated source address corresponding to the extracted address. Furthermore, the LP 115 extracts a destination address DA from the above mentioned message. If the destination address DA indicates the present station, the LP 115 replaces the VCI+VPI of each cell containing the message with a semi-permanent VCI+VPI indicating the DS1 terminating circuit 102 or the DS3 terminating circuit 104 in the present station corresponding to the destination address DA. On the other hand, if the destination address DA indicates a station other than the present station, then the LP 115 calculates an SMDS MH of the destination station, and replaces the VCI+VPI of each cell containing the above described message with a VCI+VPI pertaining to the degenerated source address and the SMDS-MH 113 of the destination station. The LP 115 also assigns information specific to an ATM method referred to as a tag to the head of each cell, which stores the above described message, so that each cell can be autonomically switched in the switch unit 108. Then, the LP 115 outputs each cell again to the switch unit 108 through the interface 114 and the highway 116.
Each switching module, not shown in the attached drawings, in the switch unit 108 switches an inputted cell at a high speed by determining the value of a tag assigned at the head of the cell.
At this time, the cell inputted from the SMDS-MH 113 is autonomically switched by the switch unit 108 according to the tag assigned to the cell if the cell is addressed to the present station. Then, it is transmitted to a subscriber in the present station via the DS1terminating circuit 102 or the DS3 terminating circuit 104, and the DS1 subscriber loop 101 or the DS3 subscriber loop 103 in the present station through multiplexer/demultiplexer 107, 106, or 105. If the cell is addressed to a station other than the present station, it is autonomically switched by the switch unit 108 according to the tag assigned to the cell. Then, it is transmitted to the SMDS-MH 113 of the destination station through the multiplexer/demultiplexer 110, a terminating circuit (FINF) 111, and a trunk circuit 112.
The LP 115 of the SMDS-MH 113 in the destination station recognizes that a message is addressed to the destination station by determining the destination address DA of the message transmitted to the destination station through a plurality of cells. Then, it replaces the VCI+VPI of each cell containing the message with a semi-permanent VCI+VPI of the DS1 terminating circuit 102 or the DS3 terminating circuit 104 in the present station corresponding to the destination address DA. Then, after assigning a tag to the head of each cell containing the message so that the cell is autonomically switched in the switch unit in the destination station, the LP 115 outputs the cell to the switch unit. After being autonomically switched in the switch unit according to the tag assigned to each cell, the cell is transmitted to a subscriber in the destination station through the DS1 terminating circuit 102 or the DS3 terminating circuit 104 via the DS1 subscriber loop 101 or the DS3 subscriber loop 103.
As described above, the DS1 terminating circuit 102 for terminating the DS1 subscriber loop 101, or DS3 terminating circuit 104 for terminating the DS3 subscriber loop 103 does not process subscriber information individually, but the SMDS-MH 113 collectively process all subscriber information, thereby reducing the cost required for the hardware of the entire switching unit and facilitating the maintenance of the unit. A control unit 109 only has to access the SMDS-MH 113 through a control line 117 in a calling process, etc., and need not access each of the DS1 terminating circuits 102 and the DS3 terminating circuits 104 separately. Thus, subscriber information can be processed effectively.
In a broadband connectionless data service such as an SMDS, etc., in addition to the above described normal cell transmission process, the function of monitoring the traffic state such as occurrences of errors, the frequency of errors, etc. must be necessarily performed by monitoring a lot of subscriber information (referred to as network parameters).
For example, a performance monitoring process is required to control the quality of a switching system, subscriber loop, terminal unit, inter-station relay line, and its interface, etc. In this process, for example, the contents of errors are monitored every fifteenth minute, and the number of the errors is notified to an operation center. The operation center recognizes the present quality according to the notification, and preliminarily maintains the quality before it indicates considerable deterioration.
Furthermore, a process referred to as a network data collection is also required. In this process, a parameter indicating the state of a switching system in specified traffic is monitored in time unit of over 15 minutes. After a subscriber has started actual communications, a larger influence is anticipated on another traffic if the predetermined amount of data processed by a subscriber has changed. Accordingly, based on a monitored parameter, each traffic is optimally planned for future use.
Since the above described performance monitoring process and network data collecting process are periodically performed for each subscriber, it is more efficient that the LP 115 in the SMDS-MH 113 shown in FIG. 1 for collectively performing subscriber information carries out the processes.
Furthermore, in a broadband connectionless data service such as an SMDS, etc., a process referred to as a special study is also required. In this process, specified subscriber information is monitored at a subscriber's request or to, according to a network provider, establish a network for future use or monitor the state of a route in which a problem will possibly occur. Each piece of subscriber information is monitored at predetermined intervals in the performance monitoring process and the network data collecting process, whereas an operator-inputted command controls the special study process according to the necessity described above.
As explained above, the special study process is not constantly performed. The process is charged with a larger load than a normal monitoring process because a monitoring process is carried out according to a command inputted by a maintenance staff for a longer time in the special study process.
Therefore, the special study process, which is not constantly performed, is charged with a larger load, and built in a normally provided SMDS MH, offers the problem that a total cost is raised, resulting in the raise of a unit cost charged for a line.
If the function of the special study process is built in the SMDS-MH 113 shown in FIG. 1, then a cost will be raised because the function should be provided for each subscriber.
On the other hand, a broadband connectionless data service such as an SMDS, etc. also requires an accounting process for each subscriber in addition to the monitoring process for a network parameter.
In an accounting process, subscriber information generated as a result of the communications of each subscriber must be collected for each subscriber individually.
In this case, account must be charged to communications data for which a network service is provided. Thus, the accounting process is performed at a destination station. Practically, the process is performed by the LP 115 in the SMDS-MH 113 (shown in FIG. 1) in the destination station.
Since a broadband connectionless data service such as an SMDS, etc. is a new network service, it has never been provided based on any accounting process. A possible accounting process is to collect and accumulate necessary subscriber information for the accounting process for each source address SA contained in a message addressed to a destination station.
However, a source address SA contained in a message is represented as, for example, 64-bit information, and the number of source addresses SA is 664 in all. It is actually impossible to accumulate such a large number of source addresses SA at each station.